ABB ASTAT® Crane motion controller Version AST10_054

Rotor control by optimising the resistance gives the motor the right characteristics The slip-ring motor torque is controlla ble at any speed by varying the external rotor resistance. Here the different speeds 92% and 57% up as well as 38% down are obtained with only varia tion of the resistance. This property has been used for many years for crane motors. When lowering with a slightly higher speed than the motors synchronous, in this example 107% of the synchronous, the motor will regenerate the energy back to the line in the most robust man ner. When the lowering speed is ap proaching the synchronous, the rotor resistor is minimised and the direction of torque changes electronically to act like a motor down. In the figure, this is shown by drawing the lowering load line, Td, for both plug braking and for regenerative lowering. For earlier generations of ASTAT controllers a compromise between the motors torque at lowest expected line voltage and lowest peak current at normal voltage was necessary.   Load line This ASTAT generation has no need for ma nual adjustment, and considers with high frequency which is the best motor character istic at this voltage Target: Not more current than necessary. The number of rotor characteristics is se lected according to the duty. ASTAT supports 1 – 5 characteristics.